US5220432A - Methods and apparatus for half-tone imaging utilizing a rotated half-tone dot map - Google Patents

Methods and apparatus for half-tone imaging utilizing a rotated half-tone dot map Download PDF

Info

Publication number
US5220432A
US5220432A US07/694,215 US69421591A US5220432A US 5220432 A US5220432 A US 5220432A US 69421591 A US69421591 A US 69421591A US 5220432 A US5220432 A US 5220432A
Authority
US
United States
Prior art keywords
map
control signal
tone dot
scanning
tone
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US07/694,215
Other languages
English (en)
Inventor
Malcolm D. M. Roe
Michael Slone-Murphy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
FFEI Ltd
Fujifilm Corp
Original Assignee
Crosfield Electronics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Crosfield Electronics Ltd filed Critical Crosfield Electronics Ltd
Assigned to CROSFIELD ELECTRONICS LIMITED reassignment CROSFIELD ELECTRONICS LIMITED ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ROE, MALCOLM DAVID MC KINNON, SLONE-MURPHY, MICHAEL
Application granted granted Critical
Publication of US5220432A publication Critical patent/US5220432A/en
Assigned to FUJIFILM ELECTRONIC IMAGING LIMITED reassignment FUJIFILM ELECTRONIC IMAGING LIMITED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CROSFIELD ELECTRONICS LIMITED
Assigned to FUJIFILM CORPORATION reassignment FUJIFILM CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FFEI LIMITED (FORMERLY FUJIFILM ELECTRONIC IMAGING LIMITED)
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4055—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern
    • H04N1/4058—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern with details for producing a halftone screen at an oblique angle

Definitions

  • the invention is concerned with the reproduction of an image in half-tone form by modulating a scanning beam in a binary manner to cause the selective exposure of portions of half-tone dots corresponding to image pixels.
  • the invention relates to methods of controlling the exposure of a record medium to a radiation beam during relative scanning movement between the medium and the beam in which an image signal representing the colour content of an image and a previously generated half-tone dot map at a particular screen angle are used to generate a binary beam control signal by scanning the map in synchronism with the beam scanning the record medium and comparing the image signal with the current map value, the binary beam control signal being generated in accordance with the result of the comparison.
  • Such methods are hereinafter referred to as of the kind described.
  • a colour component signal representing the colour component content of each pixel of the image on a grey scale is used to generate a binary beam control signal in conjunction with a half-tone dot map.
  • the map stores colour component density values at each of a number of regions which together define the full region of the dot.
  • a comparison is made between the incoming colour component signal and the corresponding dot region and depending on whether or not the image signal is greater than the value stored in the map, the beam is controlled to expose or not expose the record medium accordingly.
  • An example of this is described in DE-A-3320691 (US-A-4897736).
  • the second problem manifests itself in particular if there is a simple integer relationship between the size of the dot and the dimension of the map. In this case only a restricted subset of map locations are ever visited and this can result in a restricted number of dot sizes being available so causing contouring.
  • a typical dot at 90° may be made up of exactly 12 ⁇ 12 sub-regions each of which is exposed or not exposed by the scanning beam in accordance with the binary control signal.
  • the map may well have a different number of locations to define this region.
  • a method of the kind described is characterised in that the half-tone dot map is of a size sufficient to enable the half-tone dot map to define a number of adjacent half-tone dot areas, each area corresponding to a half-tone dot and the content of at least some areas being different; in that the half-tone dot map is scanned in the same direction and with the same increments for all screen angles; in that each area of the map is scanned to generate a control signal for corresponding areas on the record medium; and in that prior to scanning the record medium at a particular screen angle, the half-tone dot map is determined which corresponds to that screen angle.
  • an apparatus for controlling the exposure of a record medium to a radiation beam during relative scanning movement between the medium and the beam to record half-tone separations at particular screen angles comprises a control signal generator; control means; and a store for storing a previously generated half-tone dot map under the control of the control means, the control signal generator being responsive to an image signal representing the colour content of an image and a signal from the store to generate a binary beam control signal by scanning the map in synchronism with the beam scanning the record medium and comparing the image signal with the current map value, the binary beam control signal being generated in accordance with the result of the comparison characterised in that the store is of a size sufficient to enable the half-tone dot map to define a number of adjacent half-tone dot areas, each area corresponding to a half-tone dot and the content of at least some areas being different; in that the control signal generator is responsive to each area in the map for generating the control signal for adjacent, corresponding areas on the record medium; in that the control means
  • the increments are kept constant and the map itself is rotated and rescaled in accordance with the screen angle. Effectively, the X and Y increments are both made equal to one (or -1) for all screen angles and the problems mentioned above are avoided. It should be noted that this may result in a change in the size of the half-tone dot map. Furthermore, the map defines a number of half-tone dot areas.
  • the invention permits a wider range of screen angles, a greater control of screen ruling, and a much larger number of grey levels without contouring.
  • the half-tone dot map will define a square region made up of square half-tone dot areas and the sides of the square will not generally be parallel (or orthogonal) to the scanning direction. This means that during a single scan line the position in the map which is scanned correspondingly will change significantly when a border of the map is reached. This is a problem because it is often difficult to detect when the border is reached.
  • map shapes are also possible.
  • a rectangular map would require 6 parameters: K, M and N as before and K', M' and N' to specify the other side of the rectangle.
  • M'/N' should equal M/N. It is even possible to conceive of a map in the form of a parallelogram.
  • the invention is particularly suited for controlling scanning apparatus which includes a single beam but it could be adapted for use with multi-beam output scanners.
  • FIG. 1 is a block diagram of the apparatus
  • FIG. 2 illustrates an example of how the half-tone dot map would be scanned conventionally
  • FIGS. 3 and 4 illustrate modified forms of the half-tone dot map shown in FIG. 2.
  • the apparatus shown in FIG. 1 comprises a laser 1 which is responsive to a binary control signal 2 to modulate an output beam 3 to be on or off respectively depending upon the status of the control signal 2.
  • this "modulation” may be achieved by means of modulating the laser itself or by feeding the control signal to a modulator to which the laser beam is also fed continuously.
  • the beam In the "on” condition the beam is arranged to impinge on a record medium 4 mounted on a support 5.
  • the support 5 will cause the record medium 4 slowly to move in one direction while the beam 3 is caused rapidly to scan across the record medium 4 in the orthogonal direction.
  • the control signal 2 is generated from a comparator 6 to which is fed a grey level image signal defining the density of a colour component of each pixel of an image and a signal from a store 7 defining a half-tone dot value.
  • the map in the store 7 defines an array of half-tone dot areas, for example 36, each area itself defining a number of locations holding respective threshold values.
  • each individual area of the map in the store 7 is equivalent to a conventional half-tone dot map but in contrast to conventional methods, the store 7 holds a number of such maps, each typically being slightly different in terms of the threshold values which are stored.
  • the store 7 Prior to exposing the record medium, the store 7 is loaded with the map in the correct orientation and at the correct scale under the control of a suitable control device 9, such as a suitably programmed computer.
  • a suitable control device 9 such as a suitably programmed computer.
  • the directions X, Y, parallel and orthogonal to the direction of scanning of the map are always the same while the scanning increments ⁇ X, ⁇ Y are both unity, irrespective of screen angle.
  • a timing signal, or the like e.g., a clock signal, may be generated by a common clock signal generator 10 and input to the address generator 8 and to the laser source 1, as shown in FIG. 1.
  • the signal from the store 7 is selected by means of an address generator 8 which generates X,Y signals corresponding to the current position of the laser beam 3 relative to the record medium 4. In this way, the map is effectively scanned in exactly the same manner as the record medium 4.
  • FIG. 2 illustrates the orientation of a square map in store 7 defined by a number of individual half-tone dot areas, the map being positioned at an angle (the screen angle) to the direction of scanning.
  • the beam 3 will reach the position labelled A in FIG. 2 and will maintain the value X constant while decrementing the value Y by one unit at a time as the beam 3 scans along the line AB in FIG. 2.
  • the comparator 6 needs to commence accessing threshold values from position B' since effectively the map shown in FIG. 2 is repeated or tessellated across the full scanning area.
  • FIG. 3 shows how it is possible to take the square map of FIG. 2 and, by relocating two triangular sections, construct an L-shape map of the same area that will also tessalate the plane.
  • FIG. 3 applies if M is less than N. If M is greater than N then the construction is as shown in FIG. 4. It should be noted that the maximum dimension is always M+N and the other dimension is the greater of M and N.
  • the map stored in the store 7 defines a number of full half-tone dot areas and, in the case of a square map, can be defined as having dimension K by K where K is the number of dots in either direction in the map.
  • the map is thus defined by 3 parameters, K, M and N. It can be shown that to achieve ⁇ 1/2 degree precision in angle M or N need not exceed 64. Since one of the dimensions of the L-shaped map is M+N this means that the map need not exceed 128 ⁇ 128. This produces better than ⁇ 1% tolerance on the ruling.
  • the value of K will usually be chosen empirically.
  • each change of shape, ruling or angle requires a new map. This makes it desirable to generate the map contents during initialization of the output scanner. Furthermore, if all separations (typically 3 or 4) are to be imaged together then the same number of separate maps are required because it may be necessary to switch from one to another in a matter of micro seconds. In one application this means that the store 7 must contain 128 Kbytes.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Image Signal Circuits (AREA)
  • Facsimile Scanning Arrangements (AREA)
  • Fax Reproducing Arrangements (AREA)
  • Dot-Matrix Printers And Others (AREA)
  • Color, Gradation (AREA)
US07/694,215 1990-04-12 1991-04-12 Methods and apparatus for half-tone imaging utilizing a rotated half-tone dot map Expired - Lifetime US5220432A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9008318 1990-04-12
GB909008318A GB9008318D0 (en) 1990-04-12 1990-04-12 Methods and apparatus for half-tone imaging

Publications (1)

Publication Number Publication Date
US5220432A true US5220432A (en) 1993-06-15

Family

ID=10674336

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/694,215 Expired - Lifetime US5220432A (en) 1990-04-12 1991-04-12 Methods and apparatus for half-tone imaging utilizing a rotated half-tone dot map

Country Status (5)

Country Link
US (1) US5220432A (fr)
EP (1) EP0451995B1 (fr)
JP (1) JPH04227374A (fr)
DE (1) DE69113309T2 (fr)
GB (1) GB9008318D0 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5689623A (en) * 1995-03-27 1997-11-18 Optronics International Corporation Spread spectrum digital screening
US6897982B1 (en) * 1999-08-27 2005-05-24 Oki Data Corporation Image-writing device and method and image-forming apparatus reducing dot width variations in relation to a screen angle
US20070062384A1 (en) * 2003-01-14 2007-03-22 Picbags, L.P. Golf bag having image thereon, systems and methods of forming same, and methods of using golf bag
US20090261004A1 (en) * 2003-01-14 2009-10-22 Picbags, L.P. Combination System And Golf Bag

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5542029A (en) * 1993-09-30 1996-07-30 Apple Computer, Inc. System and method for halftoning using an overlapping threshold array

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3657472A (en) * 1969-01-10 1972-04-18 Hell Rudolf Dr Ing Method and apparatus for the dot-by-dot and line-by-line rastered recording of picture signals obtained by scanning picture originals with a raster rotated with respect to the recording direction
US4084183A (en) * 1970-03-18 1978-04-11 Dr. Ing. Rudolf Hell Gmbh. Method for the electro-optical reproduction of half-tone pictures
US4185304A (en) * 1977-07-07 1980-01-22 Xerox Corporation Electronic halftone screening
FR2516329A1 (fr) * 1981-11-07 1983-05-13 Dainippon Screen Mfg Procede d'enregistrement electronique d'images en demi-teintes
DE3320691A1 (de) * 1982-06-09 1983-12-15 Canon K.K., Tokyo Farbbildaufbereitungseinrichtung
FR2535477A1 (fr) * 1982-10-28 1984-05-04 Dainippon Screen Mfg Procede pour produire des points de demi-teinte dans un dispositif d'enregistrement de plaques de demi-teinte
US4447833A (en) * 1981-01-21 1984-05-08 Dainippon Screen Seizo Kabushiki Kaisha Method for producing a halftone plate
EP0293214A2 (fr) * 1987-05-29 1988-11-30 Digital Equipment Corporation Système produisant des images en demi-teintes selon des grilles asymétriques
US4969053A (en) * 1986-11-14 1990-11-06 Canon Kabushiki Kaisha A color film reading apparatus providing high-gradation color signals
EP0427380A2 (fr) * 1989-11-08 1991-05-15 Adobe Systems Inc. Procédé pour la production d'images en demi-teintes

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3657472A (en) * 1969-01-10 1972-04-18 Hell Rudolf Dr Ing Method and apparatus for the dot-by-dot and line-by-line rastered recording of picture signals obtained by scanning picture originals with a raster rotated with respect to the recording direction
US4084183A (en) * 1970-03-18 1978-04-11 Dr. Ing. Rudolf Hell Gmbh. Method for the electro-optical reproduction of half-tone pictures
US4185304A (en) * 1977-07-07 1980-01-22 Xerox Corporation Electronic halftone screening
US4447833A (en) * 1981-01-21 1984-05-08 Dainippon Screen Seizo Kabushiki Kaisha Method for producing a halftone plate
FR2516329A1 (fr) * 1981-11-07 1983-05-13 Dainippon Screen Mfg Procede d'enregistrement electronique d'images en demi-teintes
GB2111342A (en) * 1981-11-07 1983-06-29 Dainippon Screen Mfg A method for recording a halftone picture electronically
US4897736A (en) * 1982-06-09 1990-01-30 Canon Kabushiki Kaisha Color image processing apparatus using a deformed dot matrix
DE3320691A1 (de) * 1982-06-09 1983-12-15 Canon K.K., Tokyo Farbbildaufbereitungseinrichtung
FR2535477A1 (fr) * 1982-10-28 1984-05-04 Dainippon Screen Mfg Procede pour produire des points de demi-teinte dans un dispositif d'enregistrement de plaques de demi-teinte
US4543613A (en) * 1982-10-28 1985-09-24 Dainippon Screen Seizo Kabushiki Kaisha Method for producing halftone dots in a halftone plate recording apparatus
US4969053A (en) * 1986-11-14 1990-11-06 Canon Kabushiki Kaisha A color film reading apparatus providing high-gradation color signals
EP0293214A2 (fr) * 1987-05-29 1988-11-30 Digital Equipment Corporation Système produisant des images en demi-teintes selon des grilles asymétriques
EP0427380A2 (fr) * 1989-11-08 1991-05-15 Adobe Systems Inc. Procédé pour la production d'images en demi-teintes

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"An Optimum Method for Two-Level Rendition of Continuous-Tone Pictures", B. E. Bayer, Institute of Electrical and Electronics Engineers, International Conference on Communications, Jun. 11-13, 1973, Seattle, Wash., pp. 26-11-26-15, New York, 1973.
An Optimum Method for Two Level Rendition of Continuous Tone Pictures , B. E. Bayer, Institute of Electrical and Electronics Engineers, International Conference on Communications, Jun. 11 13, 1973, Seattle, Wash., pp. 26 11 26 15, New York, 1973. *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5689623A (en) * 1995-03-27 1997-11-18 Optronics International Corporation Spread spectrum digital screening
US6897982B1 (en) * 1999-08-27 2005-05-24 Oki Data Corporation Image-writing device and method and image-forming apparatus reducing dot width variations in relation to a screen angle
US20070062384A1 (en) * 2003-01-14 2007-03-22 Picbags, L.P. Golf bag having image thereon, systems and methods of forming same, and methods of using golf bag
US20070289457A1 (en) * 2003-01-14 2007-12-20 Davidson Bruce A Methods of forming images on an outer surface of a golf bag
US20090261004A1 (en) * 2003-01-14 2009-10-22 Picbags, L.P. Combination System And Golf Bag

Also Published As

Publication number Publication date
DE69113309T2 (de) 1996-03-07
EP0451995B1 (fr) 1995-09-27
GB9008318D0 (en) 1990-06-13
EP0451995A1 (fr) 1991-10-16
JPH04227374A (ja) 1992-08-17
DE69113309D1 (de) 1995-11-02

Similar Documents

Publication Publication Date Title
US4149183A (en) Electronic halftone generator
US4196451A (en) Electronic halftone generator
US5404411A (en) Bitmap-image pattern matching apparatus for correcting bitmap errors in a printing system
US5732162A (en) Two dimensional linearity and registration error correction in a hyperacuity printer
US5485289A (en) Hyperacuity printer architecture
JPH07184071A (ja) 超高感度印刷システム
US6332044B1 (en) System and method for enhancement of image contour fidelity
EP0701363B1 (fr) Procédé et appareil pour le génération de trames de points en demi-teintes pour la formation d'images en couleurs
US5479584A (en) Enhanced fidelity reproduction of images with device independent numerical sample output
EP0342845B1 (fr) Création d'images en demi-teintes
US5408329A (en) Image enhancement through digital darkness control
EP1017018B1 (fr) Procédé et appareil pour la rotation d'image à haute facilité d'adressage
EP0642258B1 (fr) Procédé pour obtenir une image tramée par modulation en fréquence
US5220432A (en) Methods and apparatus for half-tone imaging utilizing a rotated half-tone dot map
EP1439690B1 (fr) Processeur demi-tons avec sortie multi-bit échantillonée pour matrice de seuils
US5640191A (en) Resolution transforming raster based imaging system and related transformation method
EP1067763A2 (fr) Système et procédé pour obtenir des images à haute facilité d'adressage
US6320680B1 (en) Stochastic scanning documents to change moire effects
US5367381A (en) Method and apparatus for enhanced resolution and contrast via super intensity controlled overscanned illumination in a two dimensional high addressability printer
US5638110A (en) Two dimensional slope thresholding in a hyperacuity printer
US5742325A (en) Micro segmentation in a hyperacuity printer
US6798541B2 (en) Systems and methods for generating binary clustered, irrational halftone dots
JP3112308B2 (ja) 連続調整可能なラスタ解像度印刷方法
US6201560B1 (en) Multibeam modulation driver for a hyperacuity printer
US7277201B2 (en) Systems and methods for designing digital anamorphic line screens

Legal Events

Date Code Title Description
AS Assignment

Owner name: CROSFIELD ELECTRONICS LIMITED

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:ROE, MALCOLM DAVID MC KINNON;SLONE-MURPHY, MICHAEL;REEL/FRAME:005703/0070

Effective date: 19910322

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

AS Assignment

Owner name: FUJIFILM ELECTRONIC IMAGING LIMITED, ENGLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CROSFIELD ELECTRONICS LIMITED;REEL/FRAME:009138/0216

Effective date: 19980226

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12

AS Assignment

Owner name: FUJIFILM CORPORATION, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:FFEI LIMITED (FORMERLY FUJIFILM ELECTRONIC IMAGING LIMITED);REEL/FRAME:019448/0913

Effective date: 20070316